1. Field of the Invention
The present invention relates to electronic devices and methods for manufacturing electronic devices, and more particularly, to electronic devices having dielectric layers and related methods.
2. Description of the Related Art
As the integration density of semiconductor memory devices increases, the area of a cell and the space between cells decrease. However, it may be desirable that a capacitor maintain a prescribed capacitance, and thus the capacitor providing high capacitance while occupying a small area may be desired. To maintain high capacitance in capacitors occupying less substrate surface area, various measures have been suggested including using a high dielectric material for the dielectric layer, reducing a thickness of the dielectric layer, and/or increasing a surface area of a lower electrode.
Among those suggestions, both the measures of reducing a thickness of the dielectric layer and increasing a surface area of the lower electrode may have reached limits of current processing and/or physical capabilities, and thus further increases of capacitance may rely on use of dielectric materials having higher dielectric constants. A tantalum oxide (Ta2O5) film having a dielectric constant ε of 24 may be used for the dielectric layer of the capacitor. Although a dielectric layer formed of a tantalum oxide film may provide a relatively high dielectric constant, use of tantalum oxide may present new difficulties.
First, a tantalum oxide film may have an unstable chemical stoichiometric ratio due to a lack of oxygen so that an undesirable leakage current may result. To replenish the film with oxygen, a thermal oxidation may be applied to the tantalum oxide film. During the thermal oxidation, however, oxygen ions may easily penetrate the tantalum oxide film, and thus a silicon oxide film may be generated by reaction of the upper electrode with the oxygen ions at an interfacial surface between the tantalum oxide film and the lower electrode. Consequently, the effective oxide thickness of the dielectric layer (Toxeq) may increase, and the effective dielectric constant of the tantalum oxide film may decrease. Thus, the tantalum oxide film may neither reduce leakage current nor improve dielectric characteristics.